The poor little animal is now perfectly miserable. He has no protection for his tail, you see, and goes hunting about everywhere for some other shell into which he can tuck it. After a while, perhaps, he finds that of a periwinkle. It is not of much use, of course, for it is so small that he can only get just the tip of his tail into it. Still, it is better than nothing, and he goes crawling about with the periwinkle shell on the end of his tail, like a thimble on the tip of one’s finger, in search of a bigger one. By-and-by he discovers one. Then he whips his tail out of the old shell and into the new one so quickly that you can hardly see how he does it, and goes off to look for a bigger shell still. And in this way he will change his dwelling perhaps half-a-dozen times before he is really satisfied.

Sometimes you may find a hermit crab with a sea anemone fastened to the edge of the shell in which he is living. That seems strange, doesn’t it, when you remember how terribly afraid the little animal is of anemones. But in such a case the anemone never interferes with the hermit crab, and the crab never interferes with the anemone, while both of them benefit by the arrangement. The crab benefits, because no fish will ever touch him so long as an anemone is attached to his whelk-shell. There are plenty of fishes which would be quite ready to gobble him up, whelk-shell and all, if it were not for this creature. But fishes know quite well that sea anemones can sting, and therefore never think of devouring them, no matter how hungry they may be; so that so long as an anemone is guarding the whelk-shell in which he lives, the hermit knows that he is perfectly safe. And the anemone benefits, because it gets a share of the crab’s meals. When a hermit crab finds the dead body of some small creature at the bottom of the sea he pulls it to pieces and devours it; and as he does so a quantity of tiny scraps are sure to come floating upwards, and are seized by the outspread arms of the anemone. So the crab gets the big pieces, and the anemone gets the little ones; and both are perfectly satisfied.